Process of nitrating methane



Jy 4, 1939. G. K. LANDON PROCESS OF NITRATING METHANE Filed Jan; 11, 1938 METHANE VAPORIZING a MIXING cumaaa PLAT! UM. fuss MO LTEN SALT BATH QONDENSER ECEIVER INVENTOR ATTORNEY Patented July 4, 1939 o rr sr George K. Landon, Wilmington, DeL, assignmto Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application January 11, 1938, Serial No. 184,386

'7 Claims. (01. 260-644) This invention relates to the nitration of methane for formation of nitromethane.

Heretofore it has been known to nitrate paraflin hydrocarbons having from 3 to 8 carbon 5 atoms, e. g. according to the process disclosed in United- States Letters Patent No. 1,967,667. No

attempt was made to use hydrocarbons having,

more than 8 carbon atoms, nor to use the simple hydrocarbons, such as methane or ethane, which 10 have only primary carbon atoms. Later, it was disclosed in United States Letters Patent No.

" 2,071,122 that, by altering the conditions of nitration, ethane could be nitrated.

I have found that methane may be nit irated,

15 by the use of aqueous nitric acid, very simply and at good yields, by the use of the process, in ac- I cordance with this invention.

Specifically, my method of nitration of methane includes passing the reactants through the 20 heated reaction zone at high velocity and at pres- I sures from atmospheric pressure to about 800 lbs.

necessary for its formation; hence it is essential that it be removed from the hot zone very 5 rapidly.

In nitration of ethane, the best yield is obtained at a reaction temperature of about 352 C. and a contact time of the reactants at this temperature of about 9.7 seconds. Attempts to use the above conditions in nitrating methane were unsuccessful.

The method, heretofore used, of vaporizing nitric acid by bubbling the hydrocarbon through a body of nitric acid held at constant tempera- 45 ture makes it difiicult, if not impossible, to feed to the reaction zone anything except a constant boiling mixture. High'pressures are impossible,

because vaporization is prevented unless the nitric acid be raised to a temperature dangerous from the explosive point of view. My improved method avoids these disadvantages.

Furthermore, I have found that, in the nitration of methane, the presence of stainless steel causes decomposition of the nitromethane 55 formed, resulting in extremely low yields. My

improved process avoids this decomposition by the use of apparatus in which the product comes into contact with no ferrous metal, for example, apparatus of glass, glass-lined, gold, platinum, or gold-lined or platinum-lined apparatus, and produces nitromethane at satisfactory yields.

As a specific example of the carrying out of my process I pass methane, preheated to a temperature of, for example, about 500 to about 700 C., into a small chamber, through which passes a small diameter tube carrying aqueous nitric acid under pressure, said tube being preferably constructed of platinum or gold, or lined and coated therewith, said nitric acid thus being converted into vapor and escaping from the extremity of said tube into the heated methane and mixing therewith.

Said mixture of nitric acid vapor and methane may be maintained in the proportion of from about 2 to 40 mols CH4 per mol of HNOa,- preferably 1 mol HNO: to 10 mols of CH4. This mixtufe is' then passed, at a velocity represented by a contact time with reaction vessel, of about 0.005 to 1.0 second, depending upon the temperature of the reaction zone, into and through a reaction zone or apparatus, preferably comprised of a tube of Pyrex glass or any suitable metal lined with gold or platinum, maintained at a temperature within the range of about 375 C. to

about 550 0., preferably about 4(10" C. to 460 0., 80

a contact time of 0.10 second and a pressure of 100 lbs. gauge, I obtained nitromethane at a yield of 45.8%, based upon the HNOa consumed.

Further to explain the process in accordance with my invention, reference is made to the accompanying drawing in which I represents a tube through which is passed methane, heated, for example, to about 500-700 C. by a heater (not shown), passing into receiver 2, which surrounds and heats platinum pipe 3, through which passes dilute nitric acid, e. g. of 35-40% concentration. The .methane passes then into Pyrex glass coiled tube 4, and mixes with the vapors of nitric acid escaping from the end of the tube 3,,the mixture then passing through the remainder of coil 4 immersed in a bath of molten salt mixture comprising equal parts of KNOa and NaNOa, maintained at a temperature of, for example, 5

440-460 C., thence through condenser 5 and to receiver 6, where theliquid products, mainly nitromethane and nitric acid, collect and may be drawn off via valve 1 and pipe 8, while the gas products, mainly unreacted methane and nitrogen oxides, pass off via valve and pipe ID for recovery or waste. a

The bath of molten salt, Ll, contained many suitable vessel, l2,'is maintained atthe desired temperature by direct heating, submerged electrical heating units, or in any suitable manner.

Preferably, I maintain a pressure upon the reactants of about lbs. to about 800 lbs.

What I claim and desire to protect by Letters Patent is:

1. The process of nitrating methane, which includes producing contact between methane and nitric acid in a non-ferrous vessel at reaction temperature, both reactants being in the vapor phase, the time of contact in the reaction zone between the reactants being from about 0.005 to about 1.0 second and the reactants under superatmospheric pressure, rapidly removing the reaction mixture from the zone of reaction and cooling it.

2. The process of nitrating methane, which includes producing contact between methane and nitric acid at a temperature between about 375 C. and about 550 C., in a non-ferrous vessel, both reactants being in the vapor phase, the time of contact in the reaction zone between the reactants being from about 0.005 to about 1.0 second and the reactants under a pressure within the range of atmospheric to about 800 pounds, rapidly removing the reaction mixture from the zone of reaction and cooling it.

3. The process of nitrating methane, which includes producing contact between methane and nitric acid at a temperature of about 450 C. in a: non-ferrous vessel, both reactants being in the vapor phase, the time of contact in the reaction zone between the reactants being from about 0.005 to about 1.0 second and the reactants being under a pressure within the range of atmospheric to about 800 pounds, rapidly removing the reaction mixture from the zone of reaction and cooling it.

4. The process of nitrating' methane, which includes producing contact between methane and nitric acid at a temperature of about 4;60 C'. in a non-ferrous vessel, both reactants being in the vapor phase, the time of contact in the reaction zone between the reactants being about 0.10 sec- 0nd and the reactants being under pressure of about 100 pounds, rapidly removing the reaction mixture from the zone of reaction and cooling it.

5. The process of nitrating methane, which in- ,cludes producing contact between methane and nitric acid in a non-ferrous vessel, in the molar ratio of 1 nitric acid to 1'7 of methane, at a temperature of about 460 C., a contact time between the reactants of about .0.l0,second, the reactants being in the vapor phase and under a pressure of about 100 lbs., rapidly removing the reaction mixture from the zone of reaction and cooling it.

6. The process of nitrating methane which includes producing contact between methane and nitric acid while in the vapor phase in a vessel having a non-ferrous inner surface and at reaction temperature for a period of time within the range of about 0.005 second to about 1.0 second,

rapidly removing the reaction mixture from the reaction zone, and cooling it.

7. The process of nitrating methane which includesvprodueing contact between methane and nitric acid in the vapor phase in a vessel having a non-ferrous inner surface and at a temperature within the range of about 375 C. to about 550 C. for a periodof time within the range of about 0.005 second to about 1.0 second, rapidly removing the reaction mixture from the reaction zone and cooling it.

GEORGE K. LANDON. 

